Re: [Rd] R_parseVector and syntax error [was: error messages while parsing with rniParse]

From: Simon Urbanek <simon.urbanek_at_r-project.org>
Date: Thu, 18 Jun 2009 18:34:21 -0400

On Jun 18, 2009, at 17:02 , Duncan Murdoch wrote:

> Romain Francois wrote:
>> Hello,
>>
>> [I'm redirecting this here from stats-rosuda-devel]
>>
>> When parsing R code through R_parseVector and the code generates an
>> error (syntax error), is there a way to grab the error.
>> It looks like yyerror populates the buffer "R_ParseErrorMsg", but
>> then the variable is not part of the public api.
>>
>> Would it be possible to add yet another entry point to the parser
>> that would basically wrap R_parseVector so that it would have an
>> extra char* argument that would bring back the error message if
>> there is an error?
>>
>>
>
> I would oppose that. Suggest ways to reduce the complexity of the
> parser interface and I'd be interested. It's a nightmare to make
> any changes there.
>
> You can always call the R function wrapped in try(), so it's not as
> though this would give you anything that you don't already have
> access to.

I'm not quite following - we're talking about R_ParseVector in C code so the point is that the C code gets access to the error message so it can relay it to the user. There are no R-level functions involved here. The issue here for the moment is that this information is retrievable at R level but not (officially) at the C level. As for reducing complexity - technically, there is no complexity added since all this is already in place ... [adding extra char * argument to ParseVector may not be the best way but that's not what I'm arguing for]. Or am I missing something?

Cheers,
S

>
>> Romain
>>
>> Simon Urbanek wrote:
>>
>>> On Jun 15, 2009, at 12:05 , Romain Francois wrote:
>>>
>>>
>>>> Hello,
>>>>
>>>> In JRI, is there a way to get the error message that is generated
>>>> by the
>>>> parser through rniParse
>>>> For example, if I have this :
>>>>
>>>> long y = re.rniParse( "rnorm( 10 ))", 1 ) ;
>>>>
>>>> this obviously generates a parse error, so y will be the same as
>>>> (R_NilValue) :
>>>>
>>>> long null_id = re.rniEval( re.rniParse( "NULL", 1 ), 0 ) ;
>>>>
>>>> I guess the underlying question is : "Is R_ParseErrorMsg exposed to
>>>> JRI".
>>>>
>>> AFAICT R_ParseErrorMsg and friends are not exposed by the R API -
>>> they are not accessible outside, so they cannot be use by JRI. It
>>> would be nice if there was a way of accessing that info, but R
>>> doesn't currently support that.
>>>
>>> Cheers,
>>> Simon
>>>
>>>
>>>> The reason is I would like to bring back the message as part of an
>>>> exception generated when the code does not parse.
>>>>
>>>> Romain
>>>>
>>
>>
>>
>
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